Wireless communication systems are widely spread all over the world to provide various types of communication services such as voice or data. In general, the wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, etc.
Even if a bandwidth is set differently between an uplink and a downlink, only one carrier is generally considered in the conventional wireless communication system. The carrier is defined with a center frequency and a bandwidth. A multiple carrier system uses a plurality of carriers having a narrower bandwidth than a full bandwidth.
Long term evolution (LTE) based on 3rd generation partnership project (3GPP) technical specification (TS) release 8 is a promising next-generation mobile communication standard.
As disclosed in 3GPP TS 36.211 V8.5.0 (2008-12) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)”, a physical channel of the LTE can be classified into a data channel, i.e., a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH), and a control channel, i.e., a physical downlink control channel (PDCCH), a physical control format indicator channel (PCFICH), a physical hybrid-ARQ indicator channel (PHICH), and a physical uplink control channel (PUCCH).
A 3GPP LTE system supports only one bandwidth (i.e., one carrier) among {1.4, 3, 5, 10, 15, 20} MHz. The multiple carrier system uses two carriers having a bandwidth of 20 MHz to support a full bandwidth of 40 MHz, or uses three carriers respectively having bandwidths of 20 MHz, 15 MHz, and 5 MHz.
The multiple carrier system can support backward compatibility with a legacy system, and can significantly increase a data rate by using multiple carriers.
In a single carrier system, a control channel and a data channel are designed based on a single carrier. Therefore, it may be ineffective if a channel structure of the single carrier system is directly used in the multiple carrier system.
If an error occurs in a control channel when performing hybrid automatic repeat request (HARQ), HARQ buffer management may be adversely affected significantly. To avoid an HARQ buffer corruption, the control channel is generally designed in an error robust manner.
More reliable control channel transmission is necessary in the multiple carrier system which has to consider cross-carrier scheduling capable of performing scheduling between different carriers. This is because an error rate may be further increased due to a different channel state when the control channel and the data channel are transmitted using the different carriers.
Accordingly, there is a need for a technique capable of supporting the multiple carrier system.